Networking Fundamentals Flashcards

Networking Overview

  • Social Network: Collection of friends, family and coworkers for support and communication.
  • IT Network: Collection of connected devices for shared resources and communication.
  • LAN: Confined to a single geographical location.
    • SOHO
    • Enterprise LAN
    • Datacenter

Network Topologies

  • Point-to-Point: Two nodes connected.
    • Half-duplex: Cannot transmit and receive simultaneously.
    • Full-duplex: Can transmit and receive simultaneously.
  • Star: Each node connects to a concentrator.
    • Concentrator forwards signals; can be a single point of failure.
  • Mesh: Each node has a point-to-point link with every other node.
    • Formula for links: n∗(n−1)/2n*(n-1)/2
    • Partial mesh is often preferred due to complexity.

OSI Model Concepts

  • OSI Model Layers (7):
    • Application
    • Presentation
    • Session
    • Transport
    • Network
    • Data Link
    • Physical
  • Mnemonic: Please Do Not Throw Sausage Pizza Away
  • Layer 1 - Physical: Transmits bits over a physical medium.
    • Examples: Cables, hubs, repeaters, modems.
  • Layer 2 - Data Link: Transfers data between nodes on the same logical segment.
    • Encapsulation of bits into frames.
    • Examples: NIC, bridge, switch, wireless access point.
  • Layer 3 - Network: Moves data around a network of networks using IP addresses.
    • Packets are given destination IP addresses.
    • Examples: Routers, IP, ACLs, Basic Firewalls.
  • Layer 4 - Transport: Tracks communication between applications.
    • Segments data and manages each piece, reassembling at destination.
    • Examples: Multilayer switches, advanced firewalls, IDSs.
  • Layer 5 - Session: Establishes and manages connections between applications.
    • Examples: ASP, ADSP, NetBIOS, PAP.
  • Layer 6 - Presentation: Delivers data across network connections; handles encryption/decryption.
    • Examples: MIME, encryption/decryption services.
  • Layer 7 - Application: Interacts directly with end-user applications for network services.
    • Examples: SMTP, DNS, FTP.

SOHO Networks

  • Physical Layer:
    • Radio antennas for wireless.
    • RJ-45 ports for local network.
    • WAN port to connect to ISP.
  • Data Link Layer:
    • Ethernet switch.
    • Wireless access point.
    • MAC addresses for host identification.
  • Network Layer:
    • Forwards data between private network and public internet.
    • DHCP server provides IP addresses.
    • Public IP address on router's WAN interface.
  • Binary Conversion:
    • Base 10 to Binary

Troubleshooting Methodology

  • Steps:
    1. Identify the problem
    2. Establish a theory of probable cause
    3. Test the theory to determine cause
    4. Establish a plan of action
    5. Implement the solution
    6. Verify the solution
    7. Document findings, actions, and outcomes
  • Gather information by questioning users and examining system documentation.
  • Troubleshooting styles: Top-down, bottom-up, OSI Model approach.
  • Escalate if necessary (beyond knowledge, warranty, large scope, difficult customer).
  • Implement fixes and verify with both technician and customer.
  • Document findings for future reference.